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1. A group or set of four.
2. A tetravalent atom, radical, or element.
3. Biology
a. A four-part structure that forms during the prophase of meiosis and consists of two homologous chromosomes, each composed of two sister chromatids.
b. A group of four haploid cells, such as spores, formed by meiotic division of one mother cell.

[Greek tetras, tetrad-; see kwetwer- in Indo-European roots.]

te·trad′ic adj.


relating to something that has a group of four
References in periodicals archive ?
Powers, The Global Village: Transformations in World Life and Media in the 21st Century (New York: Oxford University Press, 1992): see the tetradic glossary, pp.
To put it in tetradic terms, cybernetics enhances feedback and control, obsolesces linear thinking, retrieves mythical thinking and binary logic (as contained in the skate myth and the immemorial I Ching), and, taken to an extreme, reverses into hypersurveillance.
The logic of coalition formation could be further applied on a tetradic level, for example with two allied suppliers interacting with two allied buyers.